Method of controlling the exhaust gas temperature for after-treatment systems on a diesel engine using a variable geometry turbine

ABSTRACT

A method for controlling a variable geometry turbine of a turbocharger to increase the temperature of the exhaust gas delivered to an after-treatment system. In one form the method includes reducing a fluid flow area to the turbine below a normal size and bypassing a portion of the exhaust gas around a plurality of guide vanes.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 10/840,057 filed May 6, 2004, which is a continuation-in-partof U.S. patent application No. 10/717,232 filed Nov. 19, 2003 now U.S.Pat. No. 6,931,849, which is a continuation-in-part of U.S. patentapplication Ser. No. 10/659,857 filed Sep. 11, 2003 now abandoned, whichclaims priority to British Patent Application No. 0226943.9 filed Nov.19, 2002. Each of the above applications is incorporated herein byreference.

BACKGROUND OF THE INVENTION

The present invention relates generally to a method of controlling avariable geometry turbine. More particularly, but not exclusively, thepresent invention relates to a method for controlling a variablegeometry turbocharger to affect a diesel engines exhaust gas temperatureto a desired level for after-treatment systems.

After-treatment system performance is directly related to thetemperature of the exhaust gas that passes through it. Designers ofafter-treatment systems recognize that for desired performance theexhaust gas temperature must be above a threshold temperature under alloperating conditions and ambient conditions. The threshold temperatureis generally recognized as being within a range of about 500° F. toabout 700° F. The operation of the after-treatment system below thethreshold temperature range will cause the after-treatment system tobuild up undesirable accumulations. The undesirable accumulations mustbe burnt off in a regeneration cycle to allow the after-treatment systemto return to the designed performance levels. Further, prolongedoperation of the after-treatment system below the threshold temperaturewithout regeneration will disable the after-treatment system and causethe engine to become non-compliant with government regulations.

It is recognized that the exhaust gas temperatures for the majority ofthe operating range of a diesel engine will generally be above thedesired threshold temperature. However, light load conditions and/orcold ambient temperatures often cause the exhaust gas temperature tofall below the desired threshold temperatures.

The present inventions provide a novel and non-obvious method forcontrolling the variable geometry turbocharger to increase the exhaustgas temperature to the desired threshold temperature for theafter-treatment system.

SUMMARY OF THE INVENTION

One form of the present invention contemplates a method comprising:operating a turbocharger including a variable geometry turbine having aninlet passage to the turbine with a fluid flow area, the fluid flow areahaving a normal size for an internal combustion engine operating in anormal operating range; reducing the size of the fluid flow area fromthe normal size to a reduced size for exhaust gas heating; and bypassinga portion of the exhaust gas entering the inlet passage around the guidevanes of the variable geometry turbine.

Another form of the present invention contemplates a method comprising:operating a turbocharger including a moving nozzle vane variablegeometry turbine, the turbine including an inlet passage having anexhaust gas flow area adapted for the flow of an exhaust gas, theexhaust gas flow area having a first size configured for an internalcombustion engine operating in a normal operating range; determining afirst temperature of the exiting exhaust gas of the variable geometryturbocharger; moving a nozzle ring within the variable geometry turbineto decrease the exhaust gas flow area from the first size to a reducedsize if the first temperature does not satisfy a threshold temperaturecondition; and, bypassing a portion of the exhaust gas entering theinlet passage around a plurality of vanes of the variable geometryturbine.

Yet another form of the present invention contemplates a methodcomprising: operating a turbocharger including a swing vane variablegeometry turbine having a plurality of guide vanes, the turbineincluding an inlet passage having an exhaust gas flow area adapted forthe flow of exhaust gas, the exhaust gas flow area having a first areafor an internal combustion engine operating in a normal operating range;determining a first temperature of the exhaust gas proximate the outletof the variable geometry turbocharger; swinging the plurality of guidevanes within the variable geometry turbine to reduce the size of theexhaust gas flow area from the first area to a reduced area if the firsttemperature does not satisfy a threshold temperature; and, flowing aportion of the exhaust gas entering the inlet passage around theplurality of guide vanes of the variable geometry turbine.

One object of the present invention is to provide a unique method forcontrolling a variable geometry turbocharger.

Related objects and advantages of the present invention will be apparentfrom the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional illustration of a prior art variablegeometry turbocharger including a nozzle ring.

FIG. 1 a is a schematic illustration of a turbocharger coupled in flowcommunication with an after-treatment system.

FIGS. 2 a and 2 b illustrate a modification of the turbocharger of FIG.1 in accordance with the present invention.

FIGS. 3 a and 3 b illustrate a second embodiment of the presentinvention.

FIGS. 4 a and 4 b schematically illustrate a third embodiment of thepresent invention.

FIG. 5 is an axial cross section of a swing vane variable geometryturbine with the vanes in the closed position.

FIG. 6 is an enlarged partial view of the turbine of FIG. 5 showing thevanes in the open position.

FIG. 7 is an enlarged view of the vanes in FIG. 6 showing one embodimentof the sidewalls.

FIG. 8 is an end elevation of the vanes around the turbine wheel in aclosed position.

FIG. 9 is an end elevation of the vanes around the turbine wheel in anopen position.

FIG. 10 is a sectional side elevation of another form of the presentinvention comprising troughs in one of the sidewalls.

FIG. 11 is an end elevation of the vanes in an intermediate position andshowing the troughs in a sidewall.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of promoting understanding of the principles of theinvention, reference will be made to the embodiments illustrated in thedrawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is hereby intended and alterations and modifications in theillustrated device, and further applications of the principles of thepresent invention as illustrated herein being contemplated as wouldnormally occur to one skilled in the art to which the invention relates.

Turbochargers are well known devices for supplying air to the intake ofan internal combustion engine at pressures above atmospheric (boostpressures). A conventional turbocharger essentially comprises an exhaustgas driven turbine wheel mounted on a rotatable shaft within a turbinehousing. Rotation of the turbine wheel rotates a compressor wheelmounted on the other end of the shaft within a compressor housing. Thecompressor wheel delivers compressed air to the engine intake manifold.Turbines may be of a fixed or variable geometry type. Variable geometryturbines differ from fixed geometry turbines in that the size of theinlet passageway can be varied to optimise gas flow velocities over arange of mass flow rates so that the power output of the turbine can bevaried to suite varying engine demands. The present applicationcontemplates the utilization of the present invention with all types ofvariable geometry turbines, including but not limited to moving nozzlevane and swing vane.

Conventionally, the variable geometry turbine is used to manage air flowinto the internal combustion engine under the guidance of an enginecontrol unit (ECU). A turbocharger nozzle ring is generally utilized toguide exhaust gas through the turbine stage in order to control theengine air flow delivered via the turbocharger compressor stage. Whilethe present application was developed for compression ignition dieselengines, there is also contemplated herein the application to sparkignited engines and engines running on any types of fuels be it liquidor gaseous.

Referring to FIG. 1, this illustrates a known turbocharger as disclosedin U.S. Pat. No. 5,044,880. The turbocharger comprises a turbine stage 1and a compressor stage 2. The turbine stage 1 is a variable geometryturbine comprising a turbine housing 3 defining a volute or inletchamber 4 to which exhaust gas from an internal combustion engine (notshown) is delivered. The exhaust gas flows from the inlet chamber 4 toan outlet passageway 5 via an annular inlet passageway 6 defined on oneside by a radial wall 7 of a moveable annular member 8, referred toherein as a nozzle ring, and on the other side by a facing radial wall 9of the housing 3. An array of nozzle vanes 10 extend through slots inthe nozzle ring 8 across the inlet passageway 6 from a vane support ring11 which is mounted on support pins 11 a. The arrangement is such thatthe degree to which the vanes 10 extend across the inlet passageway 6 iscontrollable independently of the nozzle ring 8 and will not bedescribed in detail here.

Gas flowing from the inlet chamber 4 to the outlet passageway 5 passesover a turbine wheel 12 which as a result drives a compressor wheel 13via turbocharger shaft 14 which rotates on bearing assemblies 15 locatedwithin a bearing housing 16 which connects the turbine housing 2 to acompressor housing 17. Rotation of the compressor wheel 13 draws in airthrough a compressor inlet 18, and delivers compressed air to the intakeof the engine (not shown) via an outlet volute 19. With reference toFIG. 1 a, there is schematically illustrated the passage of the exhaustgas from outlet passageway 5 to an after-treatment system. A variety ofafter-treatment systems as are believed generally known to one ofordinary skill in the art is contemplated herein. The types ofafter-treatment systems contemplated herein are designed to removeparticulates, nitrogen-oxide compounds, and other regulated emissions.

In one form the after treatment system includes a temperature detector2100 for determining the temperature within the after-treatment system.The temperature detector may directly determine the temperature asthough a sensor or may determine the temperature through calculationsand/or iterations in an algorithm(s) or software(s) routine(s). Thetemperature detector 2100 determines the temperature within the systemand provides a signal to the ECU to facilitate control of the variablegeometry turbine to change the exhaust gas temperature as needed.Further, the present application contemplates that the temperaturedetermination could occur at other locations such as, but not limited tothe fluid flow outlet of the turbine. It will be appreciated that thebearing housing also houses oil supply and seal arrangements, thedetails of which are not necessary for an understanding of the presentinvention.

The nozzle ring 8 comprises a radially extending annular portiondefining the radial wall 7, and axially extending inner and outerannular flanges 20 and 21 respectively which extend into an annularcavity 22 provided in the turbine housing 3. With the turbineconstruction shown in the figures, the majority of the cavity 22 is infact defined by the bearing housing 16—this is purely a result of theconstruction of the particular turbocharger to which the invention is inthis instance is applied and for the purposes of the present inventionno distinction is made between the turbine housing and bearing housingin this regard. The cavity 22 has a radially extending annular opening23 defined between radially inner and outer annular surfaces 24 and 25.A seal ring 26 is located in an annular groove provided in outer annularsurface 25 and bears against the outer annular flange 21 of the nozzlering 8 to prevent exhaust gas flowing through the turbine via the cavity22 rather than the inlet passageway 6.

A pneumatically operated actuator 27 is operable to control the positionof the nozzle ring 8 via an actuator output shaft 28 which is linked toa stirrup member 29 which in turn engages axially extending guide rods30 (only one of which is visible in the figures) which support thenozzle ring 8 via linking plates 31. However, the movement of the nozzlering 8 could be controlled by any suitable actuation means. The actuatormeans contemplated herein include, but are not limited to pneumatic,electric or hydraulic devices. Accordingly, by appropriate control ofthe actuator 27 the axial position of the guide rods and thus of thenozzle ring 8 can be controlled. FIG. 1 shows the nozzle ring 8 in itsfully open position in which the inlet passageway 6 is at its maximumwidth.

A variable geometry turbine such as that disclosed in FIG. 1 can beoperated to close the inlet passageway 6 to a minimum width when neededfor the present invention. The minimum width for the present system tocontrol exhaust gas temperatures is smaller than the minimum width fornormal engine operating conditions. More particularly, in one form theminimum width for controlling exhaust gas temperature is anticipated tobe within a range of about 0 millimeters to about 4 millimeters. Incontrast, in one form the nozzle ring 8 is generally closed to provide aminimum width/gap of about 3 millimeters to about 12 millimeters for anengine operating in the normal engine operating range. However, the sizeof the minimum widths is also generally dependent on the size andconfiguration of the turbine. In reviewing the minimum widths forengines operating in the normal range, it is appropriate to utiliseabout 25% to 100% of the maximum gap width. In setting the minimum gapwidth for controlling the heating of the exhaust gas temperature, in oneform it is appropriate to use about 0% to 25% of the maximum gap width.However, other percentages are contemplated herein. The minimumwidth/gap or throat area will be utilised herein in defining parametersrelated to the fluid flow through the annular inlet passageway 6.

FIGS. 2 a and 2 b illustrate a modification of the turbocharger of FIG.1 in accordance with the present application. Only those parts of theturbine which need to be described for an understanding of the inventionare shown in FIGS. 2 a and 2 b, which are enlargements of the nozzlering/inlet passageway region of the turbocharger showing the nozzle ringin fully open and fully closed positions, respectively. The nozzle ring8 is modified by the provision of a circumferential array of apertures32 provided through the radially outer flange 21. The positioning of theapertures 32 is such that they lie on the side of the seal ring 26remote from the inlet passageway 6 (as shown in FIG. 2 a) except whenthe nozzle ring 8 approaches the closed position, at which point theapertures 32 pass the seal 26 (as shown in FIG. 2 b). This opens bypassflow path allowing some exhaust gas to flow from the inlet chamber 4 tothe turbine wheel 12 via the cavity 22 rather than through the inletpassageway 6. The exhaust gas flow that bypasses the inlet passageway 6,and nozzle vanes 10, will do less work than the exhaust gas flow throughthe inlet passageway 6 particularly since this is turned in a tangentialdirection by the vanes 10. In other words, as soon as the apertures 32are brought into communication with the inlet passageway 6 there is animmediate reduction in the efficiency of the turbocharger andcorresponding drop in compressor outflow pressure (boost pressure) withan accompanying drop in engine cylinder pressure.

Thus, with the present invention the provision of the inlet bypassapertures 32 will have no effect on the efficiency of the turbochargerunder normal operating conditions but when the turbine is operated in anexhaust gas heating mode, and the inlet passageway is reduced to itsminimum, the apertures will 32 facilitate a greater reduction in inletpassageway size than is possible with the prior art without overpressurising the engine cylinders. More specifically, in one form of thepresent invention, the bypass apertures 32 are designed to be normallyclosed during the normal engine operating conditions.

It will be appreciated that the efficiency reducing effect on theturbocharger can be predetermined by appropriate selection of thenumber, size, shape and position of the apertures 32.

FIGS. 3 a and 3 b illustrate a second embodiment of a variable geometryturbine. As with FIGS. 2 a and 2 b, only detail of the nozzle ring/inletpassageway region of the turbine is illustrated. Where appropriate, thesame reference numerals are used in FIGS. 3 a and 3 b as used in FIGS. 1and 2. FIGS. 3 a and 3 b illustrate application of the presenttechnology to an otherwise conventional turbine, which differs from theturbine of FIG. 1 in several respects. Firstly, the nozzle vanes 10 aremounted on the nozzle ring 8 and extend across the inlet passageway 6and into a cavity 33 via respective slots provided in a shroud plate 34which together with the radial wall 7 of the nozzle ring 8 defines thewidth of the inlet passageway 6. This is a well known arrangement.

Secondly, in accordance with the teaching of European patent number 0654 587, pressure balancing apertures 35 are provided through the radialwall 7 of the nozzle ring 8 and the inner annular flange 20 is sealedwith respect to the housing 3 by a respective seal ring 36 located in anannular groove provided in the radially inner annular portion 24 of thehousing 3. The provision of the apertures 35 ensures that pressurewithin the cavity 22 is equal to the static pressure applied to theradial face 7 of the nozzle ring 8 by exhaust gas flow through the inletpassageway 6. This reduces the load on the nozzle ring with an increasein the accuracy of control of the position of the nozzle ring 8,particularly as the inlet passageway 6 is reduced towards its minimumwidth.

In view of the provision of a radially inner seal ring 36, applicationof the present invention requires provision of gas bypass passages 32 ain the inner annular flange 20 of the nozzle ring 8. The passages 32 aare positioned relative to the seal ring 26 so that they open intocommunication with the inlet passageway side of the seal ring 26 at thesame time as passages 32 b in outer annular flange 21 thereby providinga bypass flow passage through the cavity 22 achieving exactly the sameeffect as described above in relation to the embodiment of FIGS. 2 a and2 b.

Alternatively the outer passages 32 b can be omitted, relying on thepressure balancing apertures 35 to provide a bypass flow path inconjunction with inner passages 32 a.

It is also known to seal the nozzle ring with respect to the housing bylocating inner and/or outer seal rings within locating grooves providedon the nozzle ring rather than locating grooves provided within thehousing. In this case the seal ring(s) will move with the nozzle ring.Specifically, FIGS. 4 a and 4 b illustrate the nozzle ring/inletpassageway region of the turbine disclosed in European patent number 0654 587 modified in accordance with the present application. Whereappropriate, the same reference numerals are used in FIGS. 4 a and 4 bas are used above. As with the turbine arrangement of FIGS. 3 a and 3 b,the nozzle vanes 10 are supported by the nozzle ring 8 and extend acrossthe inlet passageway 6, through a shroud plate 34 and into a cavity 33.Pressure balancing apertures 35 are provided through the radial wall 7of the nozzle ring 8, which is sealed with respect to the cavity 22 byinner and outer ring seals 26 and 37. However, whereas the seal ring 26is located within a groove provided in the housing 3, the radially outerseal ring 37 is located within a groove 38 provided within the outerannular flange 21 of the nozzle ring 8 and thus moves as the nozzle ringmoves.

In accordance with the present application the inner annular flange 20of the nozzle ring 8 is provided with inlet bypass apertures 32 whichpass the seal ring 26 as the nozzle ring moves to close the inletpassageway 6 to a minimum (as illustrated in FIG. 4 b). However, theouter inlet bypass path is provided not by apertures through the nozzlering, but by a circumferential array of recesses 39 formed in the outerannular portion 25 of the opening 23 of cavity 22. As can be seen fromFIG. 4 a, under normal operating conditions the seal ring 37 will bedisposed inward of the recesses 39 preventing the passage of exhaust gasaround the nozzle ring 8 and through the cavity 22. However, as thenozzle ring moves to close the inlet passageway 6 to a minimum, as shownin FIG. 4 b, the seal ring 37 moves into axial alignment with therecesses 39 which thereby provide a bypass path around the seal ring 37to allow gas to flow through the cavity 22, and to the turbine wheel viathe inlet bypass apertures 32 provided in the inner annular flange ofthe nozzle ring 8. It will be appreciated that the effect of therecesses 39 is directly equivalent to the effect of apertures 32 andthat in operation this embodiment of the invention will function insubstantially the same way as the other embodiments of the inventiondescribed above.

It will be appreciated that modifications may be made to the embodimentsof the invention described above. For instance, if only one seal ring isrequired as for example in embodiment of FIG. 8, and this is located onthe nozzle ring, then there will be no need to provide aperture 32 inthe inner flange of the nozzle ring. Similarly, if there are both innerand outer seal rings located in the housing, it will be necessary toprovide bypass recesses in both the inner and outer annular portions ofthe housing instead of bypass apertures through the nozzle ring.

With respect to the embodiments of the present application illustratedin FIGS. 1–4, it should be appreciated that the exhaust gas flowbypassing the nozzle ring 8 is discharged into the rest of the exhaustfluid flow passing from the inlet passage in an interferingrelationship. The exhaust gas flow bypassing the nozzle ring enters theexhaust flow from the nozzle ring at a steep angle, or substantiallyperpendicularly.

With reference to FIGS. 5–11 there is illustrated a swing vane typevariable geometry turbine. The present application incorporates hereinby reference British Patent Application No. 0407978.6 filed Apr. 8,2004. A swing vane type variable geometry turbine includes guide vanesupstream of the turbine wheel that are adjustable to control thecross-sectional flow area to the turbine wheel. Turning the guide vanesso that their chords are essentially radial to the turbine wheelincreases the distance between them, the so called throat. Turning thevanes so their chords are essentially tangential to the turbine wheelreduces the throat distance between them. The product of the throatdimension and the fixed axial length of the vanes determines the flowarea of any given vane angle.

With further reference to FIGS. 5–11, there is illustrated the variablegeometry turbine comprising a turbine housing 100 including a volute orinlet chamber 200 to which exhaust gas from an internal combustionengine (not shown) is delivered. The exhaust gas flows from the inletchamber 200 to an outlet passageway 300 via an annular radially directedinlet passageway 400 defined on one side by an annular wall member 500and on the opposite side by a radially extending annular sleeve 700. Inthis annular sleeve 700 an array of circumferentially spaced vanes 800,each of which extends across the inlet passageway are supported in sucha way that they may be simultaneously rotated through rotation of alever 800 a.

Exhaust gas flowing from the inlet chamber 200 to the outlet passageway300 passes over a plurality of blades 900 a of a centripetal turbinewheel 900 and as a result torque is applied to a turbocharger shaft 1000(journaled by means of bearings 1000 a) which drives a centrifugalcompressor wheel 1100. Rotation of the compressor wheel 1100 pressurizesambient air present in an air inlet 1200 and delivers the pressurizedair to an air outlet or volute 1300 from which it is fed to an internalcombustion engine (not shown). The rotational speed of the turbine wheel900 is dependent upon the velocity of the gas passing through theannular passageway 400. For a fixed rate of flow of exhaust gas, the gasvelocity is a function of the throat width of the passageway betweenadjacent vanes, which can be adjusted by controlling the angles of thevanes 800.

With reference to FIG. 8, there is illustrated the vanes 800 in theannular inlet passageway 400 closed down to a minimum throat width. Inthe vane state set forth in FIG. 8, some of the exhaust gas bypasses thevanes 800 by flowing around the vanes through pockets and/or anygeometrical changes in the sidewalls. With reference to FIG. 9, there isillustrated the vanes 800 in a substantially open state. As the width ofthe throat between vanes 800 is reduced the velocity of the gas passingthrough them increases. The bypassing of the vanes within the inletpassageway 400 reduces the efficiency of the turbine.

The movement of the vanes 800 may be controlled by any suitableactuation means applied to the attached levers 800 a, such as, forinstance the links 1400. The vanes are preferably constrained to movetogether in unison by a ring that engages them all by the levers orinterconnecting links. A master link may be attached to an actuator (notillustrated) which could be a pneumatic, electric or hydraulic device.

With reference to FIG. 7, there is illustrated one embodiment of thepresent invention wherein one or both of the sidewalls 3000 and 3001 aretapered in an axi-symmetrical way. The taper of the sidewalls allows aportion of the exhaust gas to flow around the vanes and effectivelybypass the nozzle vane. As the vanes 800 swing from a closed state to anopen state their trailing edge moves radially inwards towards theturbine wheel inlet. The taper on the sidewall is designed so that thewidth between the sidewalls 3000 and 3001 increases the further they gettowards the turbine wheel. With reference to the embodiment of FIG. 7,there is illustrated a linear taper. However, the present invention isnot limited to linear tapers nor that both sidewalls are tapered. In oneembodiment with the vanes in the open position the clearance will be ata maximum, and as the vanes close the side clearance will be reduced tothe minimum allowable running clearance. The present inventioncontemplates that the rate of taper and the radial position of the startof the taper can be chosen to tailor the specific characteristics of theengine.

With reference to FIGS. 10 and 11 there is illustrated one embodiment ofa system having a greater degree of flexibility then the priorembodiments. The embodiment of FIGS. 10 and 11 includes a vane 800having associated therewith a discrete pocket 1500. The discrete pocket1500 can be located in one or both of the sidewalls. In one form thepockets 1500 take the substantial form of a sector over which the vanes800 sweep over as they are rotated. In one form each of the plurality ofvanes has associated therewith a pocket. The start and stop of fluidflow through the pocket 1500 can be manipulated by positioning of theleading and trailing edges of the pocket. The magnitude of the fluidflow through the pocket can be manipulated by the width and depth of thepocket. The pockets allow for the passage of a portion of the exhaustgas around the outer surface of the vane, thereby bypassing flow throughthe vanes in the nozzle stage. A variety of shapes for the pockets arecontemplated herein to meet the design parameters for the turbine. Thepockets 1500 which are generally exposed to the exhaust gas flow duringthe normal engine operating range have little effect during this periodbecause there is not created a substantially enclosed passageway aroundat least a portion of the vane. During the opening of the vanes to theexhaust gas heating location the pockets are exposed to the exhaust gasflow. A portion of the exhaust gas flows through the pockets andbypasses around the vanes 10 located within the inlet passageway 400.

The systems for some variable geometry turbines have been describedabove with reference to FIGS. 1–11. While the present application ispreferably applicable to controlling the types of variable geometryturbines described above it should be understood that the presentinventive methods are applicable to controlling a great variety of othertypes of variable geometry turbines. The present invention relies uponcontrolling the exhaust gas temperature by changing the size of theexhaust passage and bypassing a portion of the exhaust gas flow aroundthe vanes within the inlet passageway of the turbocharger.

In variable geometry turbine systems utilising a nozzle ring the nozzlering is moved axially to close down the size of the inlet passageway inresponse to the temperature within the after-treatment system beingbelow a threshold temperature. The temperature within the aftertreatment system is determined by the temperature detector. In one formthe temperature of the exhaust gas is queried at a plurality of closelytimed intervals, and in another form the detecting of temperature isalmost continuous. However, determining the time intervals for detectingare believed to be within the skill of a person or ordinary skill in theart. Upon the temperature within the after-treatment system beingdetermined to be below a threshold temperature the nozzle ring is movedaxially to an exhaust gas heating location below that required fornormal engine operation. At the exhaust gas heating location the nozzlering is maintained for a period of time until the detected temperatureis at or above the threshold temperature. With the nozzle ringpositioned at the exhaust gas heating location the bypass passages areexposed to the exhaust gas flow and exhaust gas bypasses around thebackface or under the nozzle to bypass the vanes.

The axial movement of the nozzle ring results in a decreased flow areain the inlet passageway and the uncovering of the bypass passages allowsexhaust gas to flow around the nozzle. The result is a reduction in theturbine stage efficiency and causes the airflow to be reduced andincrease the pumping work of the engine to maintain a desired powerlevel. In one form the desired power level is that level establishedprior to the determination to increase the exhaust gas temperature. Inone form the resulting exhaust gas temperature is increasedsignificantly above the threshold temperature.

With reference to the system in FIGS. 2 a and 2 b, the exhaust gas flowsfrom the inlet chamber 4 to the turbine wheel 12 via the cavity 22rather than through the inlet passageway 6. With reference to the systemin FIGS. 3 a and 3 b, the system includes passages 32 a that open intoflow communication with the inlet passageway side of seal ring 26. Theexhaust gas bypasses through the passages 32 a to the cavity 22 and fromthere to the turbine wheel 12. With reference to FIGS. 4 a and 4 b,there is illustrated a system wherein the nozzle ring moves to close theinlet passageway 6 to a minimum width for exhaust gas heating and theseal ring 37 is brought into alignment with recess 39. Therebyestablishing a bypass path around seal ring 37 to cavity 22 for passageof the exhaust gas.

With reference to the systems utilising a swing vane type variablegeometry turbine the plurality of vanes are moved in unison to closedown the size of the inlet passageway in response to the temperaturewithin the after-treatment system being below a threshold temperature.The temperature detector determines the temperature within theafter-treatment system. In one form the temperature of the exhaust gasis queried at a plurality of closely timed intervals, and in anotherform the detecting of temperatures is almost continuous. However,determining the time intervals for detecting the temperature is believedto be within the skill of a person or ordinary skill in the art. Uponthe temperature being determined to be below a threshold value the vanesare rotated to an exhaust gas heating location that defines a flow pathsmaller than is required for normal engine operation. At the exhaust gasheating location the vanes are maintained at this position until thetemperature reaches the threshold temperature. With the plurality ofvanes positioned at the exhaust gas heating location at least a portionof the exhaust gas flows around/bypasses bypassing the vanes as it flowto the turbine wheel.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiment has been shown and described and that allchanges and modifications that come within the spirit of the inventionare desired to be protected. It should be understood that while the useof the word preferable, preferably or preferred in the description aboveindicates that the feature so described may be more desirable, itnonetheless may not be necessary and embodiments lacking the same may becontemplated as within the scope of the invention, that scope beingdefined by the claims that follow. In reading the claims it is intendedthat when words such as “a,” “an,” “at least one,” “at least a portion”are used there is no intention to limit the claim to only one itemunless specifically stated to the contrary in the claim. Further, whenthe language “at least a portion” and/or “a portion” is used the itemmay include a portion and/or the entire item unless specifically statedto the contrary.

1. A method comprising: flowing an exhaust gas to a turbochargerincluding a variable geometry turbine with a nozzle ring and a pluralityof guide vanes within an inlet passage of the turbine; discharging aportion of the exhaust gas through at least one aperture in a radialface of the nozzle ring; moving the nozzle ring within the inlet passageto reduce the flow area in the inlet passage and place at least oneoutlet in the nozzle ring in flow communication with a turbine wheel;and passing the portion of the exhaust gas through the at least oneoutlet and to the turbine wheel while bypassing the guide vanes.
 2. Themethod of claim 1, wherein in said moving the nozzle ring is positionedat a location within the inlet passage to define a fluid flow area thatis smaller than a fluid flow area for normal engine operatingconditions.
 3. The method of claim 2, wherein in said passing theportion of the exhaust gas flows entirely within the turbocharger. 4.The method of claim 1, wherein in said passing the portion of theexhaust gas enters the rest of the exhaust gas flowing to the turbinewheel at one of a steep angle and substantially perpendicular thereto.5. The method of claim 1, which further includes passing exhaust gas toan after-treatment system; which further includes determining thetemperature of the exhaust gas passing to the after-treatment system;and which further includes operatively controlling said moving basedupon whether the temperature of the exhaust gas satisfies a thresholdtemperature condition.
 6. The method of claim 1, wherein the pluralityof guide vanes are fixed with the nozzle ring.
 7. The method of claim 1,wherein the plurality of guide vanes are not fixed with the nozzle ring.8. The method of claim 1, wherein the plurality of guide vanes are fixedwith the nozzle ring; wherein in said moving the nozzle ring ispositioned at a location within the inlet passage to define a fluid flowarea that is smaller than a fluid flow area for normal engine operation;which further includes passing exhaust gas to an after-treatment system;which further includes determining the temperature of the exhaust gaspassing to the after-treatment system; which further includesoperatively controlling said moving based upon whether the temperatureof the exhaust gas satisfies a threshold temperature; and wherein insaid passing the portion of the exhaust gas flows entirely within theturbocharger.
 9. A variable geometry turbocharger comprising: a housinghaving an exhaust gas inlet flow path; a turbine wheel rotatable in saidhousing; an annular nozzle ring located within said housing and having aradial wall member, an inner wall member and an outer wall member, saidradial wall member having an exhaust gas inlet opening for a passage ofexhaust gas into a volume defined by said wall members, said inner wallmember having an exhaust gas outlet; and an actuator coupled with saidnozzle ring and operable to change the position of the nozzle ringwithin said exhaust gas inlet flow path, wherein in one mode saidactuator moves said nozzle ring to an exhaust gas heating location andplaces said exhaust gas outlet in flow communication with a passagewayto said turbine wheel.
 10. The variable geometry turbocharger of claim9, wherein said passageway is defined between an inner surface of saidinner wall member and a portion of said housing.
 11. The variablegeometry turbocharger of claim 10, wherein said passageway increases theback pressure on the exhaust gas in said passageway.
 12. The variablegeometry turbocharger of claim 9, wherein the exhaust gas inlet flowpath has a maximum width, and wherein said exhaust nozzle ring when insaid exhaust gas heating location is at a location within a range ofabout zero percent to about twenty-five percent of the maximum width.13. The variable geometry turbocharger of claim 9, wherein said annularring includes a plurality of guide members connected therewith; andwherein said passageway routes exhaust gas around the plurality of guidemembers.
 14. The variable geometry turbocharger of claim 9, wherein withsaid nozzle ring at said heating location the efficiency of the turbineis reduced.
 15. The variable geometry turbocharger of claim 9, whereinsaid passageway is defined between an inner surface of said inner wallmember and a portion of said housing; wherein said passageway increasesthe back pressure on the exhaust gas flowing from said exhaust gasoutlet; wherein the exhaust gas inlet flow path has a nominal width fornormal operating conditions, and wherein said exhaust nozzle ring whenin said exhaust gas heating location defines a width for fluid flowsmaller than said nominal width; wherein said annular ring includes aplurality of guide members connected therewith; and wherein saidpassageway routes exhaust gas around the plurality of guide members. 16.A system comprising: an after-treatment system for an internalcombustion engine; a variable geometry turbocharger including a turbinehaving a housing with an exhaust gas inlet flow path and an exhaust gasoutlet flow path in fluid flow communication with said after-treatmentsystem, said turbine including a nozzle ring having a radial wall, aninner wall, and an outer wall, said radial wall having an exhaust gasinlet opening for the a passage of exhaust gas into a volume defined bysaid walls, said inner wall having an exhaust gas outlet opening forpassage of exhaust gas from said volume; and an actuator coupled withsaid nozzle ring and operable to change the position of said nozzle ringwithin said exhaust gas inlet flow path, said actuator operable to movesaid nozzle ring to reduce the size of the fluid flow area in theexhaust gas inlet flow path from a normal size for engine operation to areduced size for exhaust gas heating and place said exhaust gas outletin flow communication with said after-treatment system.
 17. The systemof claim 16, wherein said after-treatment system is a No_(x)after-treatment system.
 18. The system of claim 16, wherein said outerwall does not have an aperture for exhaust gas flow; and wherein saidnozzle ring includes a plurality of guide vanes; and the exhaust gaspassing through said exhaust gas outlet bypasses said plurality of guidevanes.